Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
Sci Rep. 2014 Feb 26;4:4206. doi: 10.1038/srep04206.
The interplay between orbital, charge, spin, and lattice degrees of freedom is at the core of correlated oxides. This is extensively studied at the interface of heterostructures constituted of two-layer or multilayer oxide films. Here, we demonstrate the interactions between orbital reconstruction and charge transfer in the surface regime of ultrathin (La,Sr)MnO3, which is a model system of correlated oxides. The interactions are manipulated in a quantitative manner by surface symmetry-breaking and epitaxial strain, both tensile and compressive. The established charge transfer, accompanied by the formation of oxygen vacancies, provides a conceptually novel vision for the long-term problem of manganites--the severe surface/interface magnetization and conductivity deterioration. The oxygen vacancies are then purposefully tuned by cooling oxygen pressure, markedly improving the performances of differently strained films. Our findings offer a broad opportunity to tailor and benefit from the entanglements between orbit, charge, spin, and lattice at the surface of oxide films.
轨道、电荷、自旋和晶格自由度的相互作用是相关氧化物的核心。这在由两层或多层氧化物薄膜构成的异质结构界面处得到了广泛研究。在这里，我们展示了在超薄（La，Sr）MnO3 的表面区域中轨道重构和电荷转移之间的相互作用，（La，Sr）MnO3 是相关氧化物的模型体系。通过表面对称破缺和拉伸和压缩两种形式的外延应变，以定量的方式操纵相互作用。所建立的电荷转移伴随着氧空位的形成，为锰氧化物的长期问题——锰氧化物的严重表面/界面磁化和导电性恶化——提供了一个概念性的新视角。然后通过冷却氧气压力有目的地调节氧空位，显著改善了不同应变薄膜的性能。我们的发现为在氧化物薄膜表面处轨道、电荷、自旋和晶格之间的纠缠提供了广泛的机会，可以对其进行调整并从中受益。
